The subject matter disclosed herein relates to turbines and, more particularly, to systems and devices for providing and improving active clearance management of turbine casings and clearances (e.g., between stationary nozzles and rotor buckets, etc.) there between during turbine operation (e.g., start-up, shut-down, etc.).
Some power plant systems, for example certain nuclear, simple cycle and combined cycle power plant systems, employ turbines in their design and operation. Some of these turbines are driven by a flow of high temperature working fluid (e.g., steam, gas, etc.) which is directed over and/or through a series of stages and components (e.g., alternating stationary and rotary airfoils/buckets/blades) within a set of casings to generate power. These casings and components may be located at close proximity (e.g., small clearances) relative to one another so as to decrease working fluid leakage through the system and improve turbine efficiency. As a result of the high temperatures of this steam during operation, the casings and components (e.g., blades, shells, rotors, etc.) experience a significant increase in temperature, often rising across a temperature range of hundreds of degrees Fahrenheit. This temperature increase may cause the components of the turbine to expand and/or contract during the various operational phases of the turbine. Casing and component expansion rates may vary depending on location, size, orientation, shape, thermal symmetries, etc., and these variances in expansion may require that clearances between the casings and components be incorporated into the design to allow for these expansion variances and prevent rubbing of components and damage to the turbine during transient periods of operation (e.g., start-up, cool-down, etc.). These clearances may compensate for the inconsistent uniform bulk section temperatures in components, particularly stationary components such as the casings, which may cause these components to deflect relative to rotating components of the turbine. However, these increased clearances may limit turbine design and steady state operation, increasing section span due to large axial clearance, reducing turbine efficiency and/or power density due to both radial and axial clearance, and allowing leakage of steam past turbine components due to large radial clearance.